The invention described herein may be manufactured and used by and for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefore.
1. Field of the Invention
The invention relates to lifting devices and is directed more particularly to a xe2x80x9cscissorsxe2x80x9d lift.
2. Description of the Prior Art
Scissors lifts are known in the art and generally include a number of scissors sections pivotally connected in a vertical array and expandable from a compressed condition and low level disposition to a relatively expanded condition and a higher level disposition. Each scissors section includes side-by-side pairs of crossed arms pivotally connected to each other at their centers and at their outer ends. They may be expanded and contracted in a bellows-like fashion.
Such lifts generally are constructed of rigid, heavy elements, otherwise the upper sections may fail to extend when extension force is applied to the lower sections. In addition, lightly constructed scissors lifts tend to be unstable, in that one side, or one of the elevator structures, rises faster than the other, causing the apparatus to sway.
There is a need for a scissors lift, which is constructed of relatively light and inexpensive material, is of relatively low weight, yet is stable and reliable.
An object of the invention is, therefore, to provide a scissors lift, which is constructed so as to provide stable and reliable operation.
A further object of the invention is to provide such a lift constructed of relatively light weight materials.
With the above and other objects in view, as will hereinafter appear, a feature of the present invention is the provision of a lift assembly having first and second elevator structures side-by-side. Each of the structures comprises a first scissors section mounted on a base bar, a second scissors section pivotally connected to the first scissors section, arms of the second scissors section being pivotally connected to each other by a lift shaft which extends between the first and second structures, at least one intermediate scissors section pivotally connected to the second scissors section, and an upper scissors section pivotally connected to an uppermost of the intermediate scissors sections and supporting a top bar. First and second side plates upstand adjacent, respectively, the first and second structures, each of the side plates having therein an elongated slot, the lift shaft being disposed in the slots. A lower pulley is mounted proximate each of the base bars on a common drive shaft. A motor for rotating the drive shaft is provided. An upper pulley is mounted proximate an upper end of each of the side plates. A strand extends from each of the lower pulleys to each of the upper pulleys, respectively, and thence to the lift shaft. The motor is operable to rotate the drive shaft, and thereby the lower pulleys, to draw in the strand from the upper pulleys which support the strand to draw the lift shaft upwardly in the side plate slots, to draw the second scissors section, and thereby remaining scissors sections, upwardly, to raise the top bar.
The above and other features of the invention, including various novel details of construction and combinations of parts, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular device embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.